inotify: make variables static in inotify_user.c

inotify_max_user_instances, inotify_max_user_watches,
inotify_max_queued_events can all be made static.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>